Abstract: A complex cavity gyrotron designed for stable operation at high order modes. The device comprises circuitry for generating an annular electron beam, a coupled cavity disposed coaxially with the electron beam and having a first and second adjacent coaxial sections with the dimensions of these coaxial sections adjusted so that different modes with the same azimuthal eigen number but different radial eigen numbers are simultaneously resonant at approximately the same frequency in the two sections, and circuitry for generating an axial magnetic field within the cavity. Few, if any, combinations of modes other than the combination chosen will simultaneously resonate in the cavity thereby effecting higher order mode suppression. The present design has a low susceptibility to beam velocity spread and is effective for any combination of modes with identical azimuthal eigen numbers.

Abstract: An RF cyclotron maser type traveling-wave amplifier including an integral active circulator. The amplifier includes a tapered interaction waveguide having a cross-section which gradually increases from a small first end to a larger second end thereof. The waveguide is capable of supporting first and second orthogonal polarization modes therein with approximately the same propagation characteristics for the two modes. A beam of mildly relativistic electrons having helical electron motion is directed into the small first end to axially propagate within the waveguide toward the larger second end. A tapered magnetic field is generated within the waveguide in a direction approximately parallel to the axis of the waveguide. The magnetic field is profiled to near grazing interaction with the second polarization mode of the waveguide. An input electromagnetic wave in the first polarization mode is launched into the larger second end of the waveguide to propagate toward the first end thereof.

Abstract: A gyromagnetron amplifier for radiation at millimeter wavelengths comprising a tapered waveguide tube with longitudinally running vanes in the walls of the tube with the number of vanes chosen to coincide with a desired cyclotron harmonic frequency to be amplified. A beam of spiralling mildly relativistic electrons with an energy of 100 keV or less is directed into the small end of the tapered waveguide tube. A tapered axial magnetic field is set up within the waveguide tube with a low value appropriate to the amplification of a cyclotron harmonic frequency. An electromagnetic wave to be amplified is launched into the waveguide tube to co-propagate and be amplified by the spiralling electron beam. This device is characterized by a wide bandwidth, a low operating magnetic field, a relatively low operating beam voltage, with high power, and the capability of continuous wave operation.

Abstract: This invention concerns a microwave generator. For the purpose of maintaining synchronism between the microwave and electrons, at high energy levels (e.g. 0.5 to 1 MeV), the first part of the generator comprises a cylindrical wave guide, the section of which increases in radius along the direction of propagation of the electron beam. Such generators can be used to obtain millimeter and submillimeter waves, with high transverse evergy (e.g. approximately 10 MeV).

Abstract: A diffraction radiation generator in which a ribbon electron beam is directed over a diffraction grating within an open resonator at a selected velocity to generate coherent radiation. After passing through the open resonator, the ribbon beam is directed through aligned slits in two or more conductive elements to a collector. Progressively negative voltages relative to the grating voltage can be applied to the elements and the collector to decelerate the electrons forming the ribbon beam and thus minimize heating of the collector and increase the operating efficiency of the generator. Also, the elements and the collector can be utilized to analyze the ribbon beam.

Abstract: The improved free electron laser device for scanning a spatial field is generally comprised of a drift tube and a rotatable mandrel. The mandrel is concentrically disposed in the tube so as to define an annular space therebetween. A series of canted mirrors of grooved-like configuration are formed about the mandrel in predetermined spaced relationship to each other and at a predetermined angle to a plane transverse of the mandrel. These mirrors function to reflect and phase redistribute various waves of the wave front so as to form a plurality of asymmetric diffraction patterns in the annular space. By reason of the nutating effect of the canted and rotating mirrors, the projected beam conically and continuously scans a region of the spatial field. In order to minimize the effect of skew waves, a series of circumferentially spaced and longitudinally extending rib-like baffles can be affixed to the tube interior between adjoining mirrors.

Abstract: A low inductance magnetic wiggler for use in electron beam type lasers generates a high intensity spatially periodic magnetic field. The wiggler is formed as a plurality of closed conductive loops having their centers spaced along a common axis. Adjacent loops are connected by a conductor extending parallel to the axis, the connecting conductors being positioned alternately on diametrically opposite sides of the loops.

Abstract: A synergistic quasi-free electron laser for generating infrared radiation. The laser includes a means for producing a volume of ionized gas plasma, a means for directing an electron beam through the gas plasma in a first direction, and a means for directing a laser pump beam into the gas plasma in a second direction opposite to the first direction to produce synergistic bunching of the electron beam and the ionized gas plasma. A portion of the laser pump beam is backscattered by the bunched electron beam and gas plasma to form an output beam having a frequency up-shifted from that of the laser pump beam. The frequency of the output beam may be tuned by changing the velocity of the electron beam.

Abstract: Radio frequency or microwave electromagnetic radiation is generated within and radiated from a cavity in response to an electron beam directed through the cavity. The electron beam is initially directed axially into the cavity and is deflected away from the axis by a time-varying field. The field may be magnetic or electrostatic and results in the radiation waves being generated as the beam deflects first to one side and then the other. Energy is reflected within the cavity, building up to provide an output pulse. The particular frequency generated is a function of the electron beam velocity and the time varying field or frequency at which the field varies.

Abstract: In the interest of increased efficiency and gain of free-electron amplifier devices, means are provided for retarding electromagnetic radiation in such devices. This permits an electron beam pulse to catch up with a pulse of electromagnetic radiation and thus to interact repeatedly with electromagnetic radiation. Retarding means may be implemented, e.g., as one or several waveguides having suitable diameter and length; alternatively, resonant filters consisting essentially of wire meshes can be used.

Abstract: A source of coherent electromagnetic radiation capable of generating or amplifying waves in the centimeter, millimeter, and submillimeter wavelength range. An annular beam of gyrating electrons is produced which is then compressed to its paraxial position by means of a solenoid magnetic field around the wave-guide. This electron beam is also subjected to a transverse motion in an interaction region by a longitudinal rippled (wiggler) magnetic field. Such a field is generated by a periodic assembly of rings magnetized in the axial direction. The electron beam during its accelerated motion generates or amplifies coherent electromagnetic radiation in the centimeter, millimeter, or submillimeter range.

Abstract: A cyclotron resonance maser microwave amplifier includes coaxial input and output waveguides. Coupling apparatus for cyclotron resonance maser microwave amplifiers and other microwave power systems is provided for transferring microwave power between first and second waveguides. Geometry permits unwanted modes to be effectively attenuated. The coupling apparatus includes first and second coaxial hollow metallic circularly cylindrical members. The first member forms a first waveguide section. A second waveguide section coaxial therewith is bounded internally by the first member, and externally by the second member. The first member has a plurality of apertures for transferring microwave power between the first and second waveguide sections. The apertures are small relative to the radius of the first member and are spaced around the circumference of the first member in a generally symmetrical array.

Abstract: An electron-beam tube for generating high microwave power at high frequencies comprises a fast-wave circuit such as a hollow waveguide. The circuit wave has a component of electric field perpendicular to its propagation axis. This field interacts with motions of the electrons transverse to the axis, in particular cyclotron rotation in an axial magnetic field. The above features are common to the well-known "gyrotrons".In the inventive tube the fast-wave circuit has means for locking a linearly polarized transverse-electric mode to the orientation of a circuit member such as the ridge in a ridged waveguide. The member (ridge) rotates spirally with distance along the guide. The added periodicity permits interaction with a space harmonic of the circuit wave. The -1 harmonic has a dispersion characteristic which provides beam-wave interaction over a wider frequency range than is possible in prior-art tubes of the gyrotron type.

Abstract: Method and apparatus for amplification of a laser pulse in a free electron laser amplifier where the laser pulse duration may be a small fraction of the electron beam pulse duration used for amplification. An electron beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f<1) of the electron beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, . . . , where substantially the same fraction f of the remainder of the electron beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron beam energy is substantially completely consumed by amplification of the laser pulse.

Abstract: Off-axis, two-dimensional designs for free electron lasers that maintain correspondence of a light beam with a "synchronous electron" at an optimal transverse radius r>0 to achieve increased beam trapping efficiency and enhanced laser beam wavefront control so as to decrease optical beam diffraction and other deleterious effects.

Abstract: Method for laser beam amplification by means of free electron laser techniques. With wiggler magnetic field strength B.sub.w and wavelength .lambda..sub.w =2.pi./k.sub.w regarded as variable parameters, the method(s) impose conditions such as substantial constancy of B.sub.w /k.sub.w or k.sub.w or B.sub.w and k.sub.w (alternating), coupled with a choice of either constant resonant phase angle or programmed phase space "bucket" area.

Abstract: A method for simultaneous amplification of laser beams with a sequence of frequencies in a single pass, using a relativistic beam of electrons grouped in a sequence of energies corresponding to the sequence of laser beam frequencies. The method allows electrons to pass from one potential well or "bucket" to another adjacent bucket, thus increasing efficiency of trapping and energy conversion.

Abstract: A storage-ring free-electron laser in which the electrons remain trapped in the optical potential wells formed by the laser fields. This is accomplished by preserving the electrons' bunched structure from pass to pass.

Abstract: A quasioptical gyroklystron for generating high power quasioptical radiation. A mildly relativistic electron beam gyrating in a static magnetic field is passed through a first open mirror resonator where a small change in the transverse electron energy takes place (either an increase or decrease depending on the relative phase between the electron gyration and the resonator wave fields). This small change than leads to slower (or more rapid) gyration of those electrons that have gained (or lost) energy in the first resonator. The length of the drift region between the first and a second open mirror resonator is adjusted so that rapidly gyrating electrons overtake slowly gyrating ones at the entrance to the second resonator. Thus the particles arrive at the second resonator strongly bunched in gyration phase. The fields in the first resonator are generated by feedback of a small amount of energy from the wave mode in the second resonator with a .pi.

Abstract: A gyrotron device e.g. a gyrotron oscillator (FIG. 3) or a gyrotron amplifier (FIG. 4) in which a circular waveguide is dimensioned to operate in a transverse electric mode (TE.sub.01) as an interaction region at an RF frequency .omega..sub.o. An injection means directs a beam of electrons, in the form of a hollow cone, into the waveguide and a solenoid generates a magnetic field, extending axially along the waveguide, which causes the electrons in the beam to gyrate at the cyclotron frequency .omega..sub.c. A solenoid coil, mounted on the side of the injection means remote from the solenoid, is used to modify the magnetic field prevailing in the vicinity of the hollow cone, to cause the field lines to extend along the electron beam.

Abstract: A gain-expanded free electron laser in which a relativistic electron beam exchanges energy with an electromagnetic wave in an interaction region defined by a magnet system is configured to suppress betatron excitation. The magnet system, the electromagnetic wave, and electron beam are characterized by a net optical phase slip qL during the interaction between the phase of the electromagnetic wave and the phase of the electron transverse velocity, and a net betatron phase advance .LAMBDA.L. The optical phase slip and the betatron phase advance are chosen to satisfy the following constraints.vertline.qL.vertline.=K.pi..vertline.qL-.LAMBDA.L.vertline.=M 2.pi.where K is an integer and M is a positive integer. These constraints suppress the excitation of the betatron motion that is excited during the pass of the electrons through the interaction region.

Abstract: A free electron laser and free electron laser amplifier using beam transport devices for guiding an electron beam to a wiggler of a free electron laser and returning the electron beam to decelerating cavities disposed adjacent to the accelerating cavities of the free electron laser. Rf energy is generated from the energy depleted electron beam after it emerges from the wiggler by means of the decelerating cavities which are closely coupled to the accelerating cavities, or by means of a second bore within a single set of cavities. Rf energy generated from the decelerated electron beam is used to supplement energy provided by an external source, such as a klystron, to thereby enhance overall efficiency of the system.

Abstract: A technique for constructing electromagnetic oscillators and amplifiers producing coherent radiation tunable from the microwave through the x-ray spectral regions. The resulting class of devices posses such novel and desirable features as broad band or narrow band operational capability in a high power and high efficiency mode. A relativistic electron beam is injected into an axial solenoidal magnetic field with a component of perpendicular motion and subsequently rotates and emits synchrotron radiation. Radiation of the proper frequency and direction will pass over the rotating beam electrons in such fashion as to cause them to lose energy to the radiation field and thus cause the intensity of the radiation field to increase. Selection of the proper radiation cavity results in laser oscillator or amplifier behavior with novel attributes.

Abstract: A gain-expanded free electron laser in which a relativistic electron beam exchanges energy with an electromagnetic wave in an interaction region defined by a magnet system is configured to suppress betatron excitation. The magnet system, the electromagnetic wave, and electron beam are characterized by a net optical phase slip qL during the interaction between the phase of the electromagnetic wave and the phase of the electron transverse velocity, and a net betatron phase advance .LAMBDA.L. The optical phase slip and the betatron phase advance are chosen to satisfy the following constraints.vertline.qL.vertline.=K.pi..vertline.qL-.LAMBDA.L.vertline.=M2.pi.where K is an integer and M is a positive integer. These constraints suppress the excitation of the betatron motion that is excited during the pass of the electrons through the interaction region.

Abstract: Apparatus for forming and utilizing a sequence of electron beam segments, each of the same temporal length (substantially 15 nsec), with consecutive beams being separated by a constant time interval of the order of 3 nsec. The beam sequence is used for simultaneous inputs to a plurality of wiggler magnet systems that also accept the laser beams to be amplified by interaction with the co-propagating electron beams. The electron beams are arranged substantially in a circle to allow proper distribution of and simultaneous switching out of the beam segments to their respective wiggler magnets.

Abstract: The invention involves a free electron laser having reduced sensitivity to variations in the energy of the input electrons. This effect is achieved by first laterally dispersing the electrons in accordance with their energies and thereafter injecting the dispersed electrons with angular and/or lateral variations to alternate polarity deflecting means.

Abstract: A high efficiency, free electron laser utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.

Abstract: A method and apparatus for constructing a continuous wave (CW) free elect laser (FEL) system capable of providing tunable high power laser radiation at short wavelengths using low-energy recirculating DC electron beams. This method replaces the static periodic magnetic field used in conventional FEL systems with an equivalently intense and continuous electromagnetic pump field having spatial periodicity less than 1 cm. The pump field is generated by a low-energy recirculated DC electron beam interacting with a transverse static periodic magnetic field.

Abstract: An apparatus and method is described for greatly enhancing the power output f a free electron laser. To enhance the electron kinetic energy that is converted to laser radiation, the wave amplification resonance condition is continuously changed along the length of the laser interaction region. The changing resonance condition is achieved by use of a static magnetic field transverse to the injected electron beam, the magnetic field having a longitudinal magnetic field gradient.

Abstract: An electrostatic free electron laser having an electromagnetic waveguide, means to produce a periodic longitudinal electrostatic field along the waveguide and an electron beam which passes through the waveguide. Radiative energy is generated by the laser as a result of the kinetic energy lost by the electron beam as it is decelerated during its interaction with the electromagnetic wave and the electrostatic field within the waveguide. In use as an oscillator, the electrostatic free electron laser includes a resonator either in addition to or instead of the waveguide.

Abstract: A magnetic field having an alternate component in a predetermined direction is produced in a zone and electrons are injected into this zone perpendicularly to said direction. To this end a winding is connected to a source for supplying current pulses having a predetermined duration. A split tube is placed coaxially within the winding and has an inner wall which provides periodic or nearly periodic variations. The split tube is formed of material having good electrical conductivity and has a skin thickness which is considerably smaller than the tube thickness at the frequency corresponding to the reciprocal of the time-duration of the current pulses.

Abstract: The generation of very high power pulses of coherent electromagnetic radiation that are continuously tunable in frequency is accomplished by means of a free electron laser in which a hollow relativistic electron beam is projected along the longitudinal axis of an evacuated drift tube. A first magnetic field expands the electron beam into an annular peripheral interaction region of the drift tube where the beam interacts with a second periodic radial magnetic field. Frequency is varied by changing the electron velocity of the electron beam or by changing the periodicity of the radial magnetic field. The device can be made to operate as an oscillator by the inclusion of resonant cavity defining mirrors within the interaction region, or as an amplifier by injecting a coherent radiation signal into the interaction region. Both oscillator and amplifier functions can be incorporated into a single device.

Abstract: A catalac free electron laser using a rf linac (catalac) which acts as a catalyst to accelerate an electron beam in an initial pass through the catalac and decelerate the electron beam during a second pass through the catalac. During the second pass through the catalac, energy is extracted from the electron beam and transformed to energy of the accelerating fields of the catalac to increase efficiency of the device. Various embodiments disclose the use of post linacs to add electron beam energy extracted by the wiggler and the use of supplementary catalacs to extract energy at various energy peaks produced by the free electron laser wiggler to further enhance efficiency of the catalac free electron laser. The catalac free electron laser can be used in conjunction with a simple resonator, a ring resonator or as an amplifier in conjunction with a master oscillator laser.